Issues with splitter cycle time after replacing cylinder

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
I have a DHT 35t splitter. Last season it started leaking oil out of the shaft seal on the ram. I knew it needed work, but in the meantime I just stored it with a metal pan under it to catch the leakage. Earlier this year I got the splitter out, cleaned everything off, changed the engine oil, and was generally giving it a once over. When actuating the cylinder, oil started spraying out of the shaft seal. Upon further examination, somehow the shaft seal manged to be "pulled out" of the cylinder, creating a hole for the oil to spray. New shaft seal needed. Aside from the leaking, everything is working normally at this time. Instead of rebuilding, I ordered a replacement cylinder and installed it last night.

In addition to replacing the cylinder, I added a couple of disconnect fittings the cylinder. They are circled in red in the photos below (except for the shaft seal, the 'blue blob', which is also circle in red). As shipped from the factory, I had to remove all hydraulic lines from the cylinder and valve in order to remove the cylinder. This means every line after the pump was essentially dry, and full of air after replacement. By adding these fittings, I should be able to remove the cylinder (in the future) without having to break all the connections to the valve. Photos attached.

After putting everything together, the cylinder is cycling extraordinarily slow. Initially it was doing the "jerky movement" thing it does, when the lines are full of air. Eventually movement became smooth, but incredibly slow. In addition, the auto-retract function of the lever/valve is not working. If I push into the auto-retract detent, it immediately comes right back out...it's not sticking at all.

DHT advertises a 12.8 second cycle time. I'm currently seeing 1:35 on ram extension, and 1:55 on ram retraction. Almost 2 minutes each way. I don't hear any abnormal noises on retraction, but I hear a squising/swooshing sound upon extension. It's similar to the sound your garden hose makes when you first start it up, and there's air running through the hose. That kind of jingling-coin, squeezing-sponge sound. I've ran the ram full extension/retraction probably 10 times now, and it doesn't seem to be speeding up. I have topped the fluid up, it's currently just below the "max" mark on the dipstick.

Is this just an issue of the oil being completely emulsified with air? If so, is there a way to speed the process up, or do I just need to let it set (possibly overnight) between ram cycles? Or is there possibly something else going on? Anything I can check/test (I do not currently have a PSI gauge on it)?
 

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jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
There are several possibilities.
Does the oil look cloudy? (air in oil)
The new cylinder could be defective and leaking by the piston seals.
The pump could be air locked and just needs to get primed.
The filter could be full. (does the filter head have a bypass on it?)

By the sound you are describing I'd guess the new cylinder is leaking past the poison. Hard to tell without being there.

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
Are you sure you got all the hoses hooked up to the correct ports on the valve?

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Are you sure you got all the hoses hooked up to the correct ports on the valve?

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
Yes. Filter hose (long) goes to top port, pump hose (short) to bottom port. The formed steel line was removed leaving the elbows in place, so no confusing the port that goes to the cylinder (and doubles as the valve mount) with the port of the steel line.

 

jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
When you extend the cylinder does it have the same force as before or will it stall when contacting the round?

(poison in above should be piston, auto correct got me)

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
When you extend the cylinder does it have the same force as before or will it stall when contacting the round?

(poison in above should be piston, auto correct got me)

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
I test split a couple of solid rounds. Split fine, just slow. I haven't put anything particularly gnarly/knotted in it.
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
I put my old cylinder back in for testing purposes. The ram extended slowly, but it would retract at normal speed (until fluid started spraying out of the seal). As I didn't want to extend it too far (due to the spray experienced when retracting it), it's possible the air wasn't bled out in the circuit that extends the ram. I also noticed the cylinder was much quieter.

I pre-filled the new cylinder, and raised each end (alternating) to get all the air out. Put it back in place, and it's exhibiting the same behavior. Slow to move, and very noisy/squealy. It would seem the issue is with the new cylinder itself. Any other suggestions on diagnostics or tests I can run?
 

jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
I'd say get it replaced. When you call for warranty they might have some tests for you to do before they replace it again.

I'm not sure about DHT cylinders but you should be able to get a rod seal for your old cylinder for very little. Same for a complete seal kit. Most hyd. cylinders are repairable.

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
FYI I've installed hundreds of dry cylinders and never had to cycle one more than four or five times to get the air out. Also, when doing this don't bottom out the cylinder, just take it back and forth about an inch or 2 short of full stroke.

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

Jags

Moderate Moderator
Staff member
Aug 2, 2006
18,087
Northern IL
You have a fluid restriction somewhere. That would explain the auto return issue as well as slow movement forward with your pressure relief valve sqealing. You added quick disconnects and a new cylinder. Start there.
 
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jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
If you look at the pics, they aren't quick disconnects, they are pipe swivels. Should be no extra restriction. Also, when he put original cylinder back on it functioned as normal. I think a defective cylinder is my best guess. Leaking by the piston seals. Hopefully when the solution is found we'll be updated.

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
As mentioned, I did put the old cylinder back on to see if the pipe swivels may have caused the issue. Old cylinder worked fine (aside from the oil leak). That seems to indicate the issue is related to the new cylinder itself.

I've since went outside and figured out how to tear the old cylinder down. It's all torn down, now I need to determine how find the appropriate seals for it.

Woodsplitter67, the "local" hydraulics shop is about an hour away. They quoted ~$280 (IIRC) to put a seal kit in it. The new cylinder was ~$270 shipped...that's why I went with the new cylinder. Figured I could learn to rebuild the old one and sell it to get some $ back, or fill it full of oil and keep it for a spare.

That plan does not seem to be working out so well.
 
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Woodsplitter67

Minister of Fire
Jan 19, 2017
1,163
Woolwich nj
As mentioned, I did put the old cylinder back on to see if the pipe swivels may have caused the issue. Old cylinder worked fine (aside from the oil leak). That seems to indicate the issue is related to the new cylinder itself.

I've since went outside and figured out how to tear the old cylinder down. It's all torn down, now I need to determine how find the appropriate seals for it.

Woodsplitter67, the "local" hydraulics shop is about an hour away. They quoted ~$280 (IIRC) to put a seal kit in it. The new cylinder was ~$270 shipped...that's why I went with the new cylinder. Figured I could learn to rebuild the old one and sell it to get some $ back, or fill it full of oil and keep it for a spare.

That plan does not seem to be working out so well.
that sucks.. it shouldn't cost that much for a rebuild. i see why you went new.. sounds like the cylinders not right. you can look up that cylinder and do the rebuild youself..
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Searching other posts, it looks like leaking cylinders is a DHT common problem. Hopefully aftermarket/replacement seals will correct it.

I'm totally unfamiliar with hydraulic cylinders...do you have any suggestions on how to look up that cylinder? Measure shaft OD, cylinder bore ID, and the OD of the other seals in the unit?
 

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jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
Don't measure. Either call DHT with your model & sn and have them send them to you or remove the seals and take them to a hydraulic shop and let them match them up. I've even UPS'd them to H&D Hydraulics in Dallas before. Usually about a 3-5 day turnaround.

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

jmb6420

New Member
Jun 25, 2019
53
NE Oklahoma
They need to send you a seal kit free with the replacement cylinder.

Lopi Endeavor
Lopi Republic
Northern tool 37t splitter
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
Long story short: User error.
Longer story below.

I decided to source seals for the old cylinder, and rebuild it while waiting to see what happened with the new one. Purchased a full set of seals for $30 or so. At reassembly, I noticed the interior of the cylinder (near the closed end) was covered in rust. Scrubbing with steel wool didn't help at all. I was able to fit a right angle mini die grinder (with abrasive pad) in there, and get most of the rust off. Still quite a bit of pitting, but knocked the sharp stuff off. Hopefully it's smooth enough for the new seals to last a while. Best I can tell, this was an air pocked formed in the cylinder due to the previous oil leak. The unit had sat a year or more leaking oil this way, and condensation/whatever must have come into play. I assume the nice cylinders are chrome plated, but being a cheap Chinese cylinder, it's just bare machined steel. So the rust took hold in the air pocket. First time rebuilding a cylinder, first time having to clean up a rusted one, so I figured I'd call it a learning experience, if nothing else.

While swapping cylinders, I noticed one of the hydraulic fittings I had installed was a 1/32" restrictor fitting. No idea how I missed this before, other than just being in a hurry and inattentive. It also was on the "loud" (during testing) end of the cylinder. No wonder the cylinder wouldn't move quickly, and was making all kinds of noise. Also makes sense why the first (blown seal) cylinder was working ok in one direction when I tested it...the blown seal was acting as a pressure release during retraction, and thus allowing it to retract at normal-ish speed.

Put the new cylinder back on to test...it worked fine. Swapped the old/rebuilt cylinder on, and it worked fine, too. So all of this was caused by inattention while swapping the new cylinder. I'm going to leave the old/rebuilt cylinder on for now, and use it. Luckily, I hadn't drained the new/replacement cylinder yet, so I just topped it off with oil (to fill it all the way up), put some PVC pipe plugs on the ports, and I'll set it aside as a spare.

Dumb mistake, but nice that I learned how easy (and inexpensive) it is to rebuild one. Also, DHT customer service was lacking during this experience...during the 3 weeks or so of dealing with this (on and off, obviously), I was only able to get 3 emails out of them. At this point, it's been 16 days since the last email I sent, when they were going to get seal part #'s for me.
 

motoguy

Burning Hunk
Jan 7, 2015
132
Central MO
You have a fluid restriction somewhere. That would explain the auto return issue as well as slow movement forward with your pressure relief valve sqealing. You added quick disconnects and a new cylinder. Start there.
This was exactly correct. I feel like an idiot for overlooking the incorrect fitting.
 

mark cline

Minister of Fire
Dec 20, 2012
637
Cattaraugus, NY
I rebuilt the both lift cylinders on my bulldozer for about $30 in seals . Hardest part was removing the nut on the end of the piston . Leaving it attached to the machine allowed me to use a big 3/4” ratchet and a 4 ft pipe for leverage